1. Field of the Invention
The invention pertains generally to video processing. In particular, it pertains to testing video process operations using a test video sequence.
2. Description of the Related Art
The use of video information has become increasingly common in recent years. Various techniques have been developed to make the video more manageable (e.g., it may be stored, it may be transmitted over the Internet or over local data channels, etc.). In these situations, storage capacity, bandwidth limitations, real time requirements, and other factors may require the video data to be processed in some manner. For example, techniques have been developed to compress digitized video data into a smaller amount of data for efficient storage and/or transmission. A corresponding decompression process is then used to obtain a reasonable copy of the original video. Such compression/decompression techniques are usually ‘lossy’, e.g., the reconstituted video is not an exact duplicate of the original because of losses inherent in the compression/decompression algorithms. Similar degradations in quality may be caused by such things as packet losses during data transmission over a network, data dropout during data transmission over a congested isochronous channel, etc.
Whatever the cause of quality degradation, test tools have been developed to measure the loss in quality by comparing the original video data with the video data after it has been processed, i.e., subjected to whatever process is being evaluated for its effects on loss of quality. However, many of these test tools have a difficult time performing an accurate comparison because both processing and testing can introduce quality losses into the video that make it difficult to identify corresponding frames for the processed and pre-processed video data. Correcting for this problem so that a proper video comparison can be made can be a difficult and error-prone operation. Further complicating the process is the fact that some types of quality loss during processing or testing are indistinguishable by human viewers (e.g., shifting the entire image up and to the right by one pixel), but show up as large differences during the comparison, thereby distorting the comparison results with quality changes that are not considered important and possibly disguising other, more subtle, quality changes that are considered important.